Abnormalities in lipid kinetics may contribute to the increased prevalence of insulin resistance and hyperlipidemia in hypertensive compared with normotensive obese persons. Therefore, we evaluated glycerol rate of appearance (a) in plasma, an index of whole-body lipolytic activity, during basal conditions and 60 minutes of epinephrine infusion after 12 h and 84 h of fasting in 6 normotensive and 6 hypertensive obese persons. Glycerol release from fat cells can be studied by stable isotope dilution mass spectrometry and is a marker of lipolysis. The data demonstrate that fat oxidation, basal whole-body lipolytic activity, and the lipolytic response to epinephrine are blunted in hypertensive compared with normotensive obese persons.